Baby growth

Baby growth charts

Within New Zealand it has always been standard practice to measure each individual baby’s growth. This is to ensure that they are growing and developing as they need to in order to reach their full potential. When slow or inadequate growth is detected early, then it can be specifically managed and corrected.

Factors which influence growth

  • Nutrition.
  • Gender.
  • Environment.
  • Genetics/familial inheritance.
  • Energy expenditure.
  • Individual physiology including healthy digestion and absorption of food.
  • Birth weight and uterine environment.

What growth charts are being used in New Zealand?

New Zealand has shown very progressive management in the way they have adopted the use of the United Kingdom – World Health Organisation Growth Charts. These were first introduced in the middle of 2010 because they show a much more realistic and optimal growth pattern for babies who are being breastfed.

These growth charts are a result of analysis of 8500 children from six different countries who were from a healthy environment and whose mothers did not smoke. Patterns and trends of weight gain and growth were analysed and as a result these charts provide an objective and more realistic comparison amongst babies of the same age and gender, including babies from New Zealand. The growth charts currently being used apply to all babies, no matter what their ethnic origins; this includes babies from European, Maori and Pacific Island descent.

These charts also have more features than the old growth charts and are assessed by the global paediatric specialist community to be the most ideal growth charts to use. You can find your baby’s growth charts in their Well Child/Tamariki Ora healthbook between pages 75-84.

N.B. All babies who are born and who have completed 37 weeks of gestation are plotted from “0” on the graph, which indicates that they were term gestation.

When will my baby’s growth be measured?

Your baby should be weighed and measured by their healthcare provider at each of their Well Child/Tamariki Ora checks. Babies need to have their length measured until they are two years of age and this needs to be done when they are in a lying down position. After the age of two, their height is measured as they stand against a wall with their feet flat on the floor and the back of their head resting on the wall. Overall growth, including length and height, needs to measured until the child is five years of age. Head circumference is routinely measured until the baby is one year of age.

If a parent or health professional has concerns about a child’s growth then more frequent measurements and plotting can be done.

What is important to remember about your baby’s growth

All babies are individual and will grow in their own unique way. Comparison is rarely useful, especially when it is done amongst very small groups of children. This is why growth charts provide the best, objective view of normal and healthy growth amongst a large number of babies and children of the same age and gender. Breastfed babies do tend to grow in a different way to babies who are formula fed. However, the new growth charts can still be used for breastfed or bottle fed babies.

After the age of two years, your child’s Body Mass Index (BMI) estimation will give an objective prediction of their health status. If your child’s BMI is in the upper range and indicates they are too heavy for their age, you will be offered information about what constitutes a healthy diet as well as some guidelines on age appropriate physical activity. The growth charts also include an adult height prediction chart, which is said to be accurate to within six centimetres.

Children’s growth changes over time and reflects other changes which are going on in their lives. New developmental or environmental changes can impact on growth. It is the pattern of growth over time which is important, rather than an isolated set of measurements and recordings. Babies will often follow the same growth curve or move to a higher curve when they are thriving. However, it is concerning when there is a dip or decrease on their weight curve, particularly if this is over two deviations or lines. Being unwell, having feeding difficulties or problems with food absorption will often be reflected in this way. When this occurs, closer monitoring and more regular weight checks are often recommended.

When considered in isolation to other factors, weight alone does not provide a good overall assessment of growth. A more complete assessment of growth can be made when it is in combination with a child’s head circumference and length. What is also important is how a child appears and how they behave, if they are reaching their developmental milestones, are generally happy and content and look healthy and well. These are all reassuring factors. Importantly, if parents are concerned about their child’s growth, then a thorough assessment is always warranted. Growth charts and the information they contain should never eclipse other clinical signs.

It is also important to remember that no two children’s growth charts will look exactly the same. Even identical twins will have some differences in their growth patterns, as will siblings measured at the same age and who have the same biological parents.

What’s included in the New Zealand baby growth charts?

  • There are nine centiles which range from the 0.4th to the 99.6th centile
  • There is no line between 0-2 weeks of age. This is because it normally takes up to two weeks for newborns to regain their birth weight. It is the presence of weight gain in comparison with their birth weight which is important in the first fortnight, rather than a comparison with other babies in this two week time- frame. *
  • The 50th centile is not emphasized as each baby has their own “normal”, rather than an ideal mean/average.
  • There is no scope for a baby’s length/height past 2 years of age.
  • For babies who were preterm, there is a separate preterm birth section within the health professional’s notes but not in the individual record. There is also an adult height prediction and BMI chart in the health professional’s notes.
  • The new charts appear different to the previous ones as the pattern of growth is based on breastfed babies. This means the weight centiles are lower than the charts whose data was predominately collected from formula fed babies.

*It is quite normal for newborn babies to lose up to 10% of their birth weight before they start regaining. If your baby’s weight loss exceeds this amount, you will be advised by your healthcare provider about what you can do.

The following charts are in the Well Child/Tamariki Ora Healthbook

  • Graph for head circumference for girls and boys 0-2 years
  • Graph for weight for girls and boys 0-1 year
  • Graph for length for girls and boys 0-2 years
  • Graph for weight for girls and boys 1-5 years
  • Graph for height for girls and boys 2-5 years

How can I interpret my baby’s growth chart?

Put simply, if 100 children of the same age and gender were all weighed and measured and these numbers were graphed, there would be a large variation between individual children. If your child’s weight was on the 10th centile, then this means that in a group of 100 children they are within a group of 10 who are either the same weight, or less and 90% of the children would weigh more.

Over time and with each health check individual measurements are joined by a continuous line. And it is the shape of this line which is important. Sudden rises or dips can be alarming and may necessitate a doctor’s assessment.

When a child is “tracking” along the same centile line from birth or gradually moving upwards to another centile it is generally a sign that the child is still growing. Weights and measurements which are taken and recorded over a longer period of time give more of an accurate picture of a child’s growth. Very frequent weighs, e.g. every week or so, can cause more alarm than reassurance. Unless you or your healthcare provider are worried about your baby’s growth then monthly weighs and measurements after the age of two weeks is the general recommendation.

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Written by Jane Barry on behalf of Huggies